Tech Corner: Big Block Engines That’ll Weigh You Down

There’s no replacement for displacement…unless that displacement is more trouble than it’s worth. Often, big block engines are like a cheat code for making power. But some models were likely better off as boat anchors than power plants. Here, we’re going to break down some of the worst big blocks on the market. Whether they are too costly to build, don’t make the necessary power, or are straight-up misleading, it’s time to pick on some big iron.

Oldsmobile 455: Time Bomb

Let’s get things rolling by taking a shot at a real contender. The Oldsmobile 455 is a legend in the automotive world and has been the heart of many iconic cars. The problem is that they simply don’t hold up. In fact, they’re notorious for blowing up. As Hot Rod Network shares, “The 455’s Achilles’ heel is a poor oil return system. The narrow passages from the stock heads do not allow oil in the valvetrain to return to the pan in an efficient manner. This condition can lead to instant death for a 455 that is run wide open for extended periods of time.”

The legendary Rocket big block still has a loyal following and holds respect among the muscle car crowd. Roadkill host, Mike Finnegan, is tickled pink when he uncovers one in the bed of a ’74 Mazda REPU mini-truck. But even he admits that “the 455 Olds, in the boating world, is what’s referred to as an ‘anchor’ because they just blow up. They’re not good motors.”

Chrysler 383 RB: Not the 383 you know…

The 383 Chrysler B engine is known as the Mopar big block that nobody loves. Typically, gearheads favor its beefier big brother, the 440. The 383 B is characterized by its large cylinder bore of 4.25 inches with a short stroke of 3.375. (That is in comparison to the 440’s 3.75.) Regardless of its under-appreciation by enthusiasts, the 383 B engine became a standard for Mopar, with over 2 million built.

Produced for a short while around the same time, however, was the 383 RB engine, a taller version of the B-engine. The RB has the opposite genetic makeup, with smaller pistons of 4.03 inches and a stroke of 3.75. The Automotive History Preservation Society explains that when a Trenton assembly line was converted in the early 1960s to produce the new Chrysler 413 engines, the demand for the 383 B was too high for the remaining lines to handle. Therefore, the 383 RB was created to fill in that gap. The overlapping timeline and similar naming of these two engines can be misleading, leading to costly mistakes for enthusiasts.

Chevy 366: Looks Can Be Deceiving

The Chevrolet big block may be the most recognized platform in the category. But if you’re going to run one, it really ought to be a 396 or 454. The 366 is a capable engine that found its home in the commercial sector, powering medium and heavy-duty trucks. A lot of people aren’t familiar with it and, when they stumble upon one in a barn or junkyard, think that because of its taller deck height, they’ve hit pay dirt. Unfortunately, while the engine boasts the same stroke as a 454, it has bores smaller than a 350. That block is only taller because it needed to fit uncommonly tall pistons.

As David Frieburger points out on Roadkill Extra, “If you run across one of these and want to build something really trick out of it, you kinda can’t … With the extra deck height, all you’re really getting is more weight, a wider intake manifold, and more aggravation.” Although, he advises that the stubby dump trucks these engines are usually housed in can make excellent parts vehicles for custom 4x4s.

Oldsmobile 403: How much are you willing to spend?

Here we have another bad boy that really is holding the short end of the stick. The Oldsmobile 403 is an engine that’s got everything going for it, in terms of bore size and stroke. However, the big block has webbed mains. This, in combination with the large bore size of 4.351 inches, really keeps the 403 from maintaining serious power. Other issues include a somewhat low compression ratio of 8:1, and costly aftermarket components (in comparison to other options). Yes, there are ways to reinforce the block. But on an engine that’s already expensive to build, the extra time and money spent on reinforcement is a real set back.

Cadillac 500: All of that for what?

More cubes means more power, right? And more power is necessary to move bigger cars. We all know that Cadillacs aren’t small–or light–vehicles, so upping the displacement of their engines to 500 cubic inches was a good decision. And that big block made some impressive power—1970 engines could produce 400 hp with 550 lb-ft of torque. But this era of production coincided with strengthening federal regulations on emissions, forcing the automaker to adapt. When the compression ratio was reduced in 1971, horsepower took a dive as well, reaching a dismal 190 hp by 1976. While the 500 engines themselves and performance parts are still available, the time and effort necessary to rebuild one often isn’t merited, as the cost-effective Chrysler 440 and the beloved Chevy 454 can pack a similar punch.

Big Block Builds

Sure, when compared to the standard of great engines like 440s, 454s, 383s and 396s, these engines tend to fall short. But that doesn’t make them all bad. In a world where technology opens infinite doors, machine shops can achieve incredible custom work, and an aftermarket is ripe with all sorts of goodies, nearly any shortcoming can be remedied. While we don’t feel these motors are a safe bet, we understand that, if done right, an oddball power plant can score way more cool points than any of the top dogs.